Velocity is vector (magnitude [speed] and direction). I assume you want the speed.
To find speed you need to know the distance traveled over time (least for average speed). Unless you are figuring out force, you don't need mass. So give me a time and I'll give you an average horizontal speed. If you truly want to find VeLoCiTy you need to know a lot more like change in y displacement and an angle and how you threw the ball.

i am guessing it is the final velocity. so the initial velocity will be zero since the object is thrown. The acceleration is 9.8m/sq. sec. And we know the distance. So using the formula V^2- u^2=2as. hence we can find the final velocity. Its best you check with some expert.

I don't think we can determine the actual velocity based on the information given. I believe you can only have an initial vertical velocity is zero if: the ball is thrown horizontally, or the ball is dropped from somewhere, or you are told it is zero. So, if we assume the ball is thrown horizontally, we still cannot determine the final vertical velocity as we do not know either how far vertically it moved, or for how long it was in the air.

As to horizontal velocity, there doesn't seem to be enough information to get an actual velocity. With all the unknowns, I think we can make a formula, but not determine the value.